One of my favorite ways to spend my free time is to kill some zombies in the apocalyptic sandbox that is Seven Days to Die. The graphics may not be great and it might have some balancing issues when it comes to difficulty relative to weapon upgrades and, yes, it has annoying glitches.
But I can forgive all that without giving it much thought, because, to put it simply, I have a lot of fun blowing the head off of some zombies in between looting sprees and house building sessions.
It just seems to hit the right combination of shooting action, incentivized exploration (better gear, weapons, etc.), and character upgradeability to keep my interest... for hours and hours on end.